Apparatus and method for reducing the number of unnecessary cuts of yarn



July 2, 1968 E. FELIX 3,390,441

' APPARATUS AND METHOD FOR REDUCING THE NUMBER OF UNNECESSARY cu'rs 0FYARN Filed Dec. 6, 1966 2 Sheets-Sheet 1 11. Fig.3 I

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APPARATUS AND METHOD FOR REDUCING THE NUMBER OF UNNECESSARY CUTS OF YARNFiled Dec. 6, 1966 2 Sheets-Sheet 2 Fig.6 H r E IN VE'NTOR EnNsT FEL 1xATTOZZEYS United States Patent Ofice 3,390,441 Patented July 2, 19683,390,441 APPARATUS AND METHOD FOR REDUCING THE NUMBER OF UNNECESSARYCUTS OF YARN Ernst Felix, Uster, Switzerland, assignor to ZellwegerLtd., Uster, Switzerland, a corporation of Switzerland Filed Dec. 6,1966, Ser. No. 599,481 Claims priority, application Switzerland, Dec.13, 1965, 17 ,249/ 65 18 Claims. (Cl. 28-64) ABSTRACT OF THE DISCLOSUREAn apparatus and method for controlling the sensitivity of a yarncleaner in dependence on the detection of a slub or double thread. Astore records whether a cut is made due to a slub or double thread andsubsequently controls the sensitivity of the yarn cleaner in dependencethereon at least during reinsertion of the cut yarn cleaner.

Usually electronic yarn cleaners are able to detect double threads inthe yarn passing through them without any particular difficulty.However, when a double thread is cut, the yarn has to be reexamined forthe presence of a double thread when replaced in the yarn cleaner sincethe cut double thread can be extremely long in some cases. Thus, a.particular problem is presented in detecting double threads after theyarn is replaced in the yarn cleaner.

Since yarns are known to undergo fairly marked variations incross-section, being non-uniform to a greater or lesser extent, doublethreads in the yarns are also nonuniform to a greater or lesser extent.If the yarn travels through a yarn cleaner at an adequate speed, forexample, at a winding speed, fluctuations in thickness can be averagedout over a fairly long section. In such a case, the mean valuecorresponds to the normal cross-section (100%) of the yarn or to twicethe normal cross-section (200%) in the case of a double thread. However,unless the yarn is introduced into the yarn cleaner, only a very shortlength is available for a cross-section measurement. In many cases, thisshort length of yarn will presumably have a cross-section ofapproximately 100%, or 200% in the case of a double thread. Due to theirregularity of the yarn, however, greater differences can occur inisolated cases. For example, a thin part of a double thread with 140% ofthe normal cross-section can he accidentally inserted into the cleaner.On the other hand, a single thread could even be inserted which, at thepoint of entry, has a thick section of 140% (+40%).

A diagram of the cross-section pattern will show that thick sectionssuch as these are by no means rare. In order to detect theaforementioned double threads, the cleaner should not be adjusted insuch a way to only respond with certainty to the insertion of a yarnwith a 200% cross-section but rather should also respond to across-section of 140%.

By contrast, the single thread is also cut in the aforementioned casedue to the accidental slub of 140% thickness. For this reason, it isimpossible to prevent a certain percentage of single threads being cutfor an almost one hundred percent detection of these double threads. Inthe case of a uniform yarn, the percentage is somewhat smaller but is alittle larger in the case of an irregular or non-uniform yarn. Althoughthe percentage can be reduced in the case of irregular yarns, byincreasing the response limit of the cleaner, the percentage of doublethreads which are not detected on introduction is thereby increased.

In comparison with the defective slubs, double threads are fairly rare.The probability of a slub and a double thread occurring simultaneouslyat the same place, is practically nil. Consequently, most cuts are madeto remove slubs in conventional cleaners which detect both slubs anddouble threads, each re-insertion is accompanied by an examination orinspection for double threads which can result in a fairly large numberof needless cuts on insertion.

Briefly, the invention relates to an apparatus and method for reducingthe number of needless cuts of yarn by yarn cleaners having adiscriminator for detecting slubs, a discriminator for detecting doublethreads and a cutting unit which reacts to a signal from eitherdiscriminator. The apparatus of the invention includes a circuitarrangement having a store or storage circuit on which at least one ofthe discriminators acts and a control member which responds to thecondition of the storage circuit. The storage circuit reacts to anoutput signal from either of the discriminators when a yarn is cut tostore the signal and to adjust the sensitivity of the double threaddiscriminator with respect to the stored signal. In addition, thestorage circuit includes a means for erasing the stored signal after theoccurrence of a subsequent predetermined signal from the slubdiscriminator or upon the re-insertion of a yarn in the cleaner.

The method of the invention includes the steps of passing a yarn througha yarn cleaner to detect the pressence of a slub or double thread byemitting signals corresponding to the presence of either. The signalsare directed to a common store for adjusting the sensitivity of the yarncleaner in dependence on the signal received whereby when a doublethread is detected the sensitivity of the yarn cleaner is adjusted to ahigh value and when a slub is detected the sensitivity is adjusted to alow value. The method also includes the step of erasing the storedsignal emitted in response to the presence of a double thread in orderto reduce the sensitivity of the yarn cleaner. This step is actuatedupon the occurrence of a signal of predetermined value in response tothe subsequent detection of a slub or upon re-insertion of the yarn inthe cleaner.

Accordingly, it is an object of the invention to reduce the number ofneedless cuts of a yarn cleaner by adjusting the sensitivity of the yarncleaner in response to the detection of slubs and double threads.

It is another object of the invention to provide a simple efiicientapparatus and method for a yarn cleaner for adjusting the sensitivity ofthe cleaner.

It is another object of the invention to store a signal in response tothe detection of a slub or double thread by a yarn cleaner and to adjustthe sensitivity of the yarn cleaner in response to the stored signal.

It is another object of the invention to erase the above stored signalcorresponding to the detection of a double thread upon subsequentdetection of a slub in order to. lower the sensitivity of the yarncleaner.

These and other objects and advantages of the invention will become moreapparent from the following detailed description and appended claimstaken in conjunction with the accompanying drawings in which:

FIG. 1 graphically illustrates the frequency of occurrence of slub anddouble thread thicknesses in a yarn;

FIG. 2 illustrates a block diagram of a conventional yarn cleaner;

FIG. 3 illustrates a block diagram of a yarn cleaner incorporating astore according to the invention;

FIG. 4 schematically illustrates a circuit arrangement for a slubdiscriminator;

FIG. 5 schematically illustrates a circuit arrangement for a doublethread discriminator;

FIG. 6 schematically illustrates a circuit arrangement for a store ofthe invention; and

FIG. 7 schematically illustrates a common circuit arrangement for sluband double thread discriminators and a store.

Referring to FIG. 1, the frequency of occurrence of the distribution ofcross-sectional frequencies of a single yarn 10 and a double yarn 20 areplotted with the cross sectional values Q as the abscissa in percentageof the average cross-section and the relative frequencies f for each ofthe cross-sectional values Q are plotted as the ordinates. The greatestfrequency for single yarns is found at Q=100% while the greatestfrequency for double yarns or threads is found at Q=200%.

Thus, if the response limit of a yarn clearner is set at 200% for doublethreads, then only 50% of the double threads passing through the yarncleaner are detected while all the double threads of an overallcross-section less than 200% (in this case, 50% of all double threadscorresponding to the overall frequency at 200%) are ignored. On theother hand, only those slubs which take up 200% of the normalcross-section are separated out although their frequency is extremelylow. If, by contrast, the response limit of the yarn cleaner is set at100%, every single yarn with a cross-section of 100% and more is cut,i.e. 50% of all cases. In this instance, all but 0.2% of all the doublethreads are detected since, according to the statistical distribution,only 0.2% of all double threads have an overall cross-section of lessthan 100% of the normal cross-section. However, such high sensitivity isnot desired because it reduces production very considerably.

It is possible, however, to find a suitable compromise by setting theresponse limit of the yarn cleaner at 140% for example. In this case,the number of needless cuts is reduced to On the other hand, the numberof double threads which are not cut increases to 5%. While thepercentage of needless cuts reaches the generally acceptable limit withsuch a response limit, the percentage of double threads which are notout still remains excess1ve.

Referring to FIG. 2, a yarn cleaner for the detection both of slubs anda double threads of a yarn 1 has a measuring head 2 for passage of theyarn 1 in which associated amplifiers (not shown) may also beaccommodated. The yarn cleaner includes a discriminator 3 for slubswhich emits a signal to a cutting unit 5 when a slub passes through anda discriminator 4 for double threads which likewise emits a signal tothe cutting unit 5 when a double thread passes through.

Referring to FIG. 3, a yarn cleaner, as above, additionally incorporatesa store 6 according to the invention which is controlled by at least oneof the two discriminators 3, 4 and acts upon the sensitivity of thediscriminator 4 depending upon the storage condition. The sensitivitylevel could, of course, also be varied elsewhere, for example, in anamplifier accommodated in the measuring head 2. As already mentioned,sensitivity must be controlled at least during the insertion orintroduction phase of the yarn. In order to achieve this object variousmodifications are possible both in the manner in which the store iscontrolled and in the manner in which the store is erased. For example,the signal generated by the discriminator 3 can be retained in the store6, in which case the sensitivity of the discriminator 4 can be loweredfor the double thread channel. Alternatively, it is possible for thesignal generated by the discriminator 4 to be retained in the store 6and the sensitivity of the discriminator 4 increased since itssensitivity is normally fairly low. If, however, a cut is initiated by adouble thread, the sensitivity of discriminator 4 is increased. Asalready mentioned there are numerous alternatives for erasing the storedsignal. Also, the store 6 can be controlled both by the discriminator 3and by the discriminator 4, in which case the sensitivity of thediscriminator 4 is reduced where the store 6 is controlled by thediscriminator 3, and increased where it is controlled by thediscriminator 4.

Referring to FIG. 4, discriminator 3 for detecting slubs consists of aconventional Schmitt trigger which releases a signal at an output 22when a predetermined input voltage is exceeded at an input 21.

Referring to FIG. 5, one example of a discriminator 4 for double threadsconsists of an RC-section and a Schmitt trigger. The RC-section has aninput 31 which permits only signals for coarse or double threads to passand the Schmitt trigger only releases a signal at an output 32 when apredetermined output voltage of the RC-section is exceeded.

Referring to FIG. 6, a store circuit arrangement consists of aconventional bistable multivibrator wherein the inputs 41, 42 of thebistable multivibrator are connected to the outputs 22, 32 of thediscriminators 3 and 4. If, therefore, a double thread, for example,passes through the measuring head, the discriminator 4 releases a signalat output 32 and hence at the input 41 of the bistable multivibratormaking input transistor 43 conductive. The signal at one of thecollectors of the bistable multivibrator can then be used forsensitivity control.

Referring to FIG. 7, a circuit arrangement incorporates not only adiscriminator 3, discriminator 4 and store 6, as above, but also usescertain elements in common. For example, a transistor 55 acts as anoutput transistor both for the discriminator 3 and the discriminator 4.On the other hand, the inputs of the transistors 51 and 53 are stillindependent of one another so that the circuit is as it were formed bytwo Schmitt triggers with separate inputs but a common output. Thebistable multivibrator is also included in this circuit and consists ofthe transistors 52 and 54 and of the resistances 56, 57, 58 and 59. Inthis case, the multivibrator is directly controlled by the collectorcurrents of the input transistors 5Land S3.

The circuit arrangement of FIG. 7 operates as follows. If, for example,a slub appears, a corresponding ON-signal is generated at the input 41and the transistor 53 becomes conductive. As a result, the transistor 54also becomes conductive, and remains conductive even after the signal atthe input 41 has disappeared thereby blocking the transistor 53. If, onthe other hand, a double thread appears, the transistor 51 becomesconductive, as does the transistor 52 which also remains conductive evenafter the signal at the input 31 has disappeared. The response limit orsensitivity of the Schmitt trigger can be varied by means of theresistances 56 and 57. If, for example, the resistance 56 is greaterthan 57, the sensitivity of the Schmitt trigger is higher when thetransistor 52 is conductive. Accordingly, the required objective isachieved because there is an increase in sensitivity on the arrival of adouble thread. The sensitivity remains high until a sufiiciently largesignal appears at the input 41, as a result of which the transistor 53or 54 becomes conductive and the bistable multivibrator flips, i.e. thesensitivity is lowered again after the arrival of a slub.

Although the required objective is in principle obtained with circuitsin which the discriminator 3 erases the store 6, circuits of this kindare attended by a disadvantage. For example, if a yarn bobbin runs outof yarn, no cut can be made. Accordingly, the discriminator 4 isadjusted to a low sensitivity level. However, if a new yarn bobbincontains a double thread immediately at the beginning, the double threadis not detected on account of the inadequate sensitivity level. Thisdisadvantage can be obviated by controlling the store 6 only by thediscriminator 3, i.e. by lowering the sensitivity of the' discriminator4 after the discriminator 3 has been triggered by a slub. A signal cannow be received, as is known per se by the measuring head 2incorporating an amplifier, indicating whether a yarn 1 is passingthrough. This signal erases the signal retained in the store.

As far as the textile industry is concerned, the following propertiesare obtained by the latter arrangement described. If a yarn is cut dueto the presence of a slub, the sensitivity level is low upon replacementof the yarn so that hardly any needless cuts are made. As mentioned, theprobability of a slub and a double thread occurring simultaneously isvery small so that the reduction in sensitivity is quite permissible.When the thread passes through the yarn cleaner again, the store iserased. If a cut is made due to the presence of a double thread, or if anew yarn bobbin has to be inse1ted, the sensitivity of the discriminator4 is relatively high and the probability of double threads not beingdetected correspondingly small. Naturally, a certain percentage ofneedless cuts must be expected although, as explained, this ispermissible.

The circuit arrangement shown in FIG. 7 is a very detailed example of acircuit. The circuit has only to be amplified or supplemented in such away that the signal indicating the passage of a thread which can beobtained in known manner from the A.C. voltage signal of the threadpassing through, makes the transistor 54 conductive or blocks thetransistor 52. This can be done by a positive impulse at the base of thetransistor 54 or by a negative impulse at the base of the transistor 52,depending upon the polarity of the aforementioned signal. Instead ofbeing erased by the signal released by the thread passing through, thesignal contained in the store 6 may even be erased by the impulsegenerated upon insertion of the yarn. It could also be erased after acertain time interval particularly in cases where, following a cut, theyarn travels normally again within a predetermined time, for example, inthe case of automatic winding machines.

Having thus described the invention it is not intended that it be solimited as changes may be made therein without departing from the scopeof the invention. Accordingly, it is intended that the subject matterdescribed above and shown in the drawings be interpreted as illustrativeand not in a limiting sense.

What is claimed is:

1. In combination with a yarn cleaner having a measuring head forpassage of a yarn therethrough, a first discriminator for detecting thepresence of a slub in the yarn in said head and emitting a signal inresponse thereto, a second discriminator havin an adjustable sensitivityfor detecting the presence of a double thread in the yarn in said headand emitting a signal in response thereto, and a cutting device forreceiving a signal from one of said discriminators to cut the thread; astore operatively connected to said first and second discriminators forreceiving said signals therefrom, said store including a circuitarrangement responsive to a signal from at least one of saiddiscriminators for storing the signal received and a control element foradjusting the sensitivity of said second discriminator in response tothe signal stored in said circuit arrangement.

2. The combination as set forth in claim 1 wherein said discriminatorsare each Sch-mitt triggers.

3. The combination as set forth in claim 1 wherein said discriminatorsand said store have a common output.

4. The combination as set forth in claim 1 wherein said store is abistable multivibrator.

5. The combination as set forth in claim 4 wherein said bistablemultivibrator includes means for erasing the stored signal to flip saidbistable multivibrator back to an initial position.

6. The combination as set forth in claim 5 wherein said means isactuated after a predetermined period of time after storing of thestored signal.

7. The combination as set forth in claim 5 wherein said means isactuated upon emission of a predetermined "signal from said firstdiscriminator.

8. The combination as set forth in claim 5 wherein said means isactuated upon emission of an A0. voltage signal from said measuring headin response to re-insertion of the yarn.

9. A method for reducing the number of needless cuts in an electronicyarn cleaner having an adjustable sensitivity to emit signals inresponse to the presence of slubs and double threads of predeterminedsize in a yarn passing therethrough comprising the steps of receiving asignal in response to the presence of a slub or double thread ofpredetermined size, storing said received signal, and

adjusting the sensitivity of the yarn cleaner in response to said storedsignal to emit signals in response to subsequent double threads ofdifferent size than the predetermined size.

10. A method as set forth in claim 9 wherein the sensitivity of the yarncleaner is determined by a signal emitted on the presence of a slub.

11. A method as set forth in claim 9 wherein the sensitivity of the yarncleaner is increased upon storing a signal responsive to a doublethread.

12. A method as set forth in claim 9 wherein the sensitivity of the yarncleaner is reduced upon storing a signal responsive to a slub.

13. A method as set forth in claim 9 which further includes the step oferasing the stored signal to return the sensitivity of the yarn cleanerto the initial sensitivity.

14. A method as set forth in claim 13 wherein said step of erasingoccurs after a predetermined time period.

15. A method as set forth in claim 13 wherein said step of erasingoccurs upon re-insertion of the yarn in the yarn cleaner.

16. A method as set forth in claim 13 wherein said step of erasingoccurs upon emission of a subsequent signal corresponding to a slub.

17. A method as set forth in claim 13 wherein said step of erasing isactuated by an AC. voltage signal upon further passage of the yarn.

'18. A method as set forth in claim 13 wherein said step of erasing isactuated by an externally applied impulse.

References Cited UNITED STATES PATENTS 3,187,568 6/1965 Gonsalves et al.73-160 3,258,824 7/1966 Gith 2864 3,309,754 3/1967 Metcalf 28-643,326,481 6/ 1967 -Frickert 242--36 LOUIS K. RIMRODT, Primary Examiner.

